This invention relates to bioreactors, and more particularly, to fixed bed macroporous carrier culture high density generating systems.
Retroviral vectors are generally produced from producer cells grown in two-dimensional monolayer systems such as T-flasks, roller bottles, and other monolayer cell culture systems. Most of these systems have multiple processes for large-scale production. The number of cells is limited by the surface area of the culture system which limits the level of vector titer achievable with these systems. Also, extended stable vector production is difficult after cells reach 100% confluence in these systems, because of the possible detachment of cells from the culture surfaces.
Fixed bed porous glass sphere bioreactors for animal cells are known. For example, reference is made to an article A fiber-Bed Bioreactor for Anchorage Dependent Animal Cell Cultures: Part I. Bioreactor Design and Operation by Chiou et al., Biotechnology and Bioengineering, Vol. 37, Pp. 755-761 (1991). Disclosed is a bioreactor comprising an inner draft tube and an annular packed glass fiber bed. Cells are immobilized on the glass fibers in the annular region, and medium fills both the draft tube and the annular region. Air is introduced from the base of the tube and oxygenates the medium in the draft tube, and bubbles disengage at the upper fluid surface. The density difference between the aerated fluid in the draft tube and the bubble-free liquid in the annular fiber bed leads to global circulation of the medium in the bioreactor. The problem with this arrangement as recognized by the present inventors is one of efficient cell production and scale-up effectiveness. While the above article discloses high scale-up potential is expected, such scale-up is a function of the axial extent of the draft tube and annular region of glass fibers which is believed to be limited. Also, the medium flow through the fibers is only axial which is also believed to be limiting with respect to efficiency of culture production.
A second bioreactor system is disclosed in an article entitled Fixed Bed Porous Sphere (Porosphere) Bioreactors for Animal Cells by Looby et al., Cytotechnology 1: 339-346 (1988). Disclosed is a bioreactor in which solid glass spheres are replaced with open pore glass spheres. However, scale-up of the disclosed system is believed limited for reasons similar to those mentioned above in the Chiou article in that both systems disclose axial medium flow in the packed bed. Such prior art systems are limited in scale-up by the build up of pressure and nutrient gradients within the packed bead bed both axially and radially.